It is known that a modified polypropylene is more compatible with nylon than an unmodified polypropylene. U.S. Pat. No. 3,484,403 and J. App. Poly. Sci., Vol. 18, pp. 963-974. Thermoplastic elastomeric compositions comprising blends of polypropylene and cured hydrocarbon rubbers (e.g., U.S. Pat. Nos. 4,104,210 and 4,130,535) and those comprising blends of nylon and cured nitrile rubber (U.S. Pat. No. 4,173,556) are known.
It was postulated that mixing a blend of polypropylene and cured hydrocarbon rubber with a blend of nylon and cured nitrile rubber would give a composition having properties that neither of the individual blends possessed alone. For example, the multicomponent blend would exhibit better oil resistance than the polypropylene/hydrocarbon rubber blend and better heat aging than the nylon/nitrile rubber blend. However, when such a mixture was prepared, the resulting composition exhibited poor stress-strain properties, especially low strength and low elongation. If the stress-strain properties could be improved, then valuable compositions would be obtained.